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GEOG 111: TEST 2
Clouds
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are of the atmosphere that's saturated or supersaturated, millions or billions of microscopic size water droplets
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Warm clouds
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Temp of environment is > -10 degrees C
-consist exclusively of water droplets (water has hard time freezing in thin air)
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Cold Clouds
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temp of environment is < -10 degrees C
-consist largely of ice crystals
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Clouds distinguished on basis of...
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-altitude
- pattern
- ability to produce precipitation
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height |
cirro- high level clouds
alto- mid-level clouds
- largely cold
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Pattern
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cumulo- vertically developed
-associated w/ convection
strato- stratified
-featureless, no vertical development
-cold and warm clouds
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Precipitation
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nimbo- precipitation bearing
- cold and warm clouds
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Cirrus |
thin, wispy clouds
At least 18,000 ft. in atmosphere
ALWAYS below -10 C
Most common are cirrus
Not very dense or thick
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Cirrocumulus |
high level
-little bit of vertical development
*fine grained pattern, tiny patches of blue sky in btwn tiny clouds
- indicates there's some instability there (vertical motion--> cloud)
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Cirrostratus
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typically cover most or large amount of sky
thin
low density
sun can shine through
Sometimes create ring around sun/moon ("sun dogs": pattern where like is diffracted into diff colors )
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Contrails
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Commercial airlines create these (20,000-40,000 ft.)
"con"= condensation
water vapor out of plan creates deposition (vapor--> ice crystals)
-Esp. common in Midwest
-makes it less likely to cool down at night
-more common in winter
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Altocumulus
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vertical development (similar to cirrocumulus)
slightly larger than cirrocumulus
-seems bigger b/c closer to the observer
-Convection
-Air sinks in blue patches of sky
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Altostratus |
VERY similar to cirrostratus
Not very thick, sun can shine through
Sun is much dimmer coming through these clouds
Little more density than cirrostratus (more ice crystals)
*Gradual lowering of clouds
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Status clouds
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can produce drizzle, not measurable
not very thick, usually thick enough to block out sun completely
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Nimbostratus |
Usually darker (b/c thicker)
featureless as falling precipitation obscures cloud edges
thicker stratified clouds
little darker than stratus clouds
less sunlight can come through
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Stratocumulus
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air that rises convectively, lifts and can't lift anymore so it sinks some
-layered clouds, look little like cumulus clouds
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Cumulus
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• Common with daytime heating when the relative humidity is relatively high (e.g. summer in the Carolinas).
-Rise a bit higher than other cumulus clouds
-Clear indication of convection, instability in atmosphere
-Esp. common during day (like in afternoon hours, b/c it’s the warmest so ELR is steepest) -Moist air masses allow lifting to happen and create cumulus
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Cumulonimbus
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-Keep developing and getting taller until they transition into a cumulonimbus clouds -Very little light can get through it
-After gets to tropopause (temp starts to get warmer (inversion))- atmosphere becomes very stable (loses buoyancy)à spreads out (creates anvil, elliptical or circular appearance)
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Super cell storm
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rotating
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Precipitation
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• Requires the development of droplets/snowflakes that are 100 times bigger than cloud water droplets/ice crystals
Need saturated environment
sustained enough lifting (so droplets/crystals can get big enough to form rain/snow)
Cloud water droplets much smaller than raindrops (must grow)
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Bergeron
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grows ice crystals through multiple processes involving all 3 states of water
-requires a cold cloud
SEE CHART in powerpoint
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Air Pressure (P)
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force exerted by air across a unit area
measured by Barometer
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Isobar
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line on weather map that connects points that have the same atmospheric pressure
-low & high pressure systems tell us what weather will be like
-close together= rapid changes in air pressure, very windy
-far apart: lighter winds
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Low pressure systems assoc. w/
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inclimate weather
Cyclone:
converging toward lower pressure
-counterclockwise winds
rising
--> clouds, precipitation
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high pressure systems assoc. w/
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inclimate weather
Cyclone:
converging toward lower pressure
-counterclockwise winds
rising
--> clouds, precipitation
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Density |
mass/volume
- amount of mass contained in a given volume of a substance
-smaller volume- molecules hitting each other more--> higher density
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Temperature
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in a confined space v= constant
not constant in atmosphere
in ideal gas law: inc. temp--> inc. pressure (& opposite)
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Compressing/ expanding atmosphere
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gets cooler-->contracts
warmer--> expands
warming column: bottom will dec. in air pressure, top will increase in air pressure
in cooling column: increase in air pressure at bottom, top decrease in pressure
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Relationship between temp and surface pressure
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negative
Day: warmer
Night: cooler
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Relationship between temp and pressure aloft
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positive
Day: air pressure higher aloft
Night: air pressure at surface increase
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Warm & Cold air column chart
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SEE CHART
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Monsoon
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very wet season followed by a very dry season
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Sea-land breeze
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day: land warms faster than water, higher pressure over the water
(wind from ocean-->land)
--brings lot of moisture--> it's convected
Night: water warmer, land higher pressure
(win from land--> ocean)
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Valley-mtn breeze
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from valley up into the mountains
happens during the day n this picture
air rising- lower pressures on mountains (cumulus clouds form over mtns)
Mtn breeze- men into valley
happens at night
air is pulled down the mtn slope (gravity)
valleys very cold at night
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Pressure gradient PG
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affects wind
primary factor (really generates the wind)
-gradient- change in a quantity per unit in a distance
- as PG increases, the wind speed increases
-usually in mb/ 100 km
-tornadoes have strongest pressure gradient in weather
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Coriolis Effect
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- moving objects to turn towards the right (left) in the Northern (Southern) Hemisphere.
-stronger in higher latitudes
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Geostrophic wind
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wind that blows parallel to isobars, well above the earth's surface
-surface complicates the wind (trees, buildings, etc. slow the winds down, decreases Coriolis effect)
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Friction
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resistance to air flow associated w/ surface roughness
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gust factor
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low gust factor- very consistent winds
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wind fetch
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distance over which winds can blow unimpeded
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Bernoulli effect
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the fact that winds can funnel their way through narrow passages
wind gap: winds funnel through the gap, blow faster
Bernoulli effect
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pollutant
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airborne particles and gases that occur in concentrations that endanger the health and well being of organisms
ex. dust, volatile organic compounds (VOCs) from vegetation (ex. haze in smoky mtns)
sulfur dioxide from volcanoes
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Primary pollutants
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released directly from the surface
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secondary pollutants
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chemical reactions w/ primary pollutants
*summer: lots of ozone created in atmosphere (made during day, max. in late afternoon)
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Air pollution trends
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downward
air cleaner now than used to be
EPA, filters, more efficient cars
Average globally: much higher (China, India)
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Air pollution sources
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concentrated in red areas of map (SEE MAP)
scattered across south
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wind speed weakest
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night or early morning
(faster during cool season, March windiest month)
Winds move downstream and spread out (disperse)
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subsidence inversion
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broad areas of atmosphere wind is sinking (warming up)
-reaches point and can't sink anymore
-Much higher than nocturnal radiation inversion
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Bermuda High
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largely responsible for mid-level subsistence in the Carolina
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Adiabatic processes
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change in temp of air, no addition or subtraction of heat
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Lifting Condensation level (LCL)
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height that air must be lifted in which to bring it to saturation
-marine environment: don't have to lift very much, so lower LCL's
-increases throughout day
-slightly higher over cities vs. rural areas
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Convective Uplift
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buoyant air parcels rise as they remain relatively warmer ( & less dense) than their surroundings
-almost every day it's sunny this occurs
- usu. happens on sides of lake (b/c air over water is cooler and isn't rising)
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Instability
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has propensity for convection to occur
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What is stability based on?
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the lapse rates
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Environmental Lapse rate (ELR)
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the rate of change of temperature w/ height in the atmosphere
-always changing
-varies w/ space & time
-varies according to weather features in the area (ridges, troughs, clouds, etc.)
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Dry adiabatic lapse rate (DALR)
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rate of change of temp in a rising DRY air parcel
-usually around 10 degrees C
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Wet adiabatic lapse rate (WALR)
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rate of change of temp in a rising SATURATED air parcel
-usu. 5-6 degrees C
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